1. Field
The embodiments relate to a power reduction device for backing up data stored in a cache memory and the like.
2. Description of the Related Art
In recent years, with an increase in capacity of storage devices such as a magnetic disk device (HDD) and a magneto-optic disk device (MO), a capacity of a cache memory that transmits and receives data to/from such devices has been increasing. Such a cache memory is incorporated in, for example, a disk array device, and data in the memory in case of power failure is saved in, for example, a disk device.
FIG. 6 is a diagram for explaining the aforementioned process in case of power failure. Usually, a power source is supplied from the outside of a device to power source units 30 and 31, and the power source is supplied to controllers 32 and 33 in the device to charge battery units 34 and 35. For example, in case of power failure in this state, a power supply from the outside is stopped, and consequently, the power supply to the power source units 30 and 31 is lost.
Monitoring units 36 and 37 detect this state, notify the controller 32 and 33 of generation of the power failure, and instruct the battery units 34 and 35 to supply (discharge) a backup power source.
FIG. 7 shows a circuit diagram of the aforementioned controller 32 (or 33) Usually, the power source unit 30 (or 31) supplies the power source to individual power sources 40 and 41 in the controller 32 (or 33). However, in case of the aforementioned power failure, the power source is supplied from the battery unit 34 (or 35). For example, the individual power source 40 supplies the power source to central processing units (referred to as CPU) 42 and 43 and a chipset 44, and the individual power source 41 supplies the power source to a dual in-line memory module (referred to as DIMM) 45 that is a cache memory.
In addition, a channel adapter 46 shown in the same drawing transmits and receives data via a communication circuit to/from a host apparatus such as a personal computer, and a controller monitoring block 47 monitors a state in the controller 32 (or 33). Furthermore, a backup medium 48 stores data of the DIMM 45 in case of power failure.
However, in the known power supply method for data backup, a power is supplied to controllers etc. even in case of power failure; and consequently, consuming power is not changed from normal consumption. Therefore, when data save time in case of power failure is lengthened, a large power is required, which leads to, for example, upsizing of a battery unit and an increase in number of the battery units.